Reasons
1. Generalised sensation (-all the teeth) - attrition , abrasion , root sensitivity due to recession of gums - use any antisensitivity paste( ex themoseal , vantej, sensodyne ) for the same
2. Localised (particular teeth or side ) - visit a dentist
Reason may be cavity in teeth which needs professional help
If the issue is painful due to heat n cold intake
Again may need professional help
Next Steps
U may start with anti sensitive paste to gauge the magnitude of issue